Steam power plant

ABSTRACT

An inventive steam power plant comprises at least one steam turbine and a steam generator, whereby a combustion chamber, in the direction of the flow of steam, is mounted after a first turbine stage and before a second turbine stage of the steam turbine, and the flow of steam inside a combustion chamber can be heated by mixing it with a hot gas that can be produced inside said combustion chamber.

CROSS REFERENCE TO RELATED APPLICATION

This application is the US National Stage of International Application No. PCT/EP2004/008348, filed Jul. 26, 2004 and claims the benefit thereof. The International Application claims the benefits of German Patent application No. 20313279.3 DE filed Aug. 27, 2003, both of the applications are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention relates to a steam power plant with at least one steam turbine and a fired steam generator.

BACKGROUND OF THE INVENTION

With known steam power plants operating steam for a steam turbine is generally generated in a fired steam generator, with the energy contained in a hot gas being transferred to one or more heat exchangers, which are supplied with water, such that operating steam can be generated by heating this water, or which are supplied with steam such that superheating of the steam can be achieved by means of a last-mentioned heat exchanger; such superheating takes place in known steam turbines for example between a high-pressure stage and a medium-pressure stage of the steam turbine, with the steam leaving the high-pressure stage being superheated by means of an intermediate superheating heating surface disposed in the steam generator and being supplied to the medium-pressure stage.

Such intermediate superheating of the steam for example contributes to the greater efficiency of the steam turbine.

With known steam power plants the thermal energy for the generation and/or intermediate superheating of steam is supplied by means of heat exchanger surfaces, which are disposed in the fired generator, for example a coal, oil or biomass-fired or generally fossil or nuclear-fired steam boiler and come into contact with a hot gas supplied in the steam generator. The heated heat exchanger surfaces in turn transfer their thermal energy to water and/or steam, which is/are supplied inside the element formed by a heat exchanger surface. Heating therefore takes place by means of a heat transfer from the hot gas to the heat exchanger surface and from the heat exchanger surface to the medium to be heated.

Since with the heat exchangers known from the prior art, which are used in steam generators of known steam power facilities, the energy from a hot gas is transferred to the medium to be heated by means of a material of the heat exchanger surface heated by the hot gas, the quantity of energy that can be transferred to the medium to be heated, for example water and/or steam, is limited by the material characteristics of the heat exchanger surface.

With known steam power facilities the permissible steam temperatures are therefore limited, since the heat exchanger surface transferring the thermal energy cannot be heated up to an arbitrary high temperature due to its material characteristics and the thermal load limits associated therewith.

The thermal transfer of hot gas to the medium to be heated is also subject to a delay, essentially due to the time required to heat up the heat exchanger surface.

SUMMARY OF THE INVENTION

The object of the invention is therefore to specify a steam power plant with at least one steam turbine and a steam generator, which can be used in a flexible manner and in particular overcomes the disadvantages of the prior art as mentioned above.

According to the invention the object is achieved by a steam power plant, comprising at least one steam turbine and a fired steam generator, whereby a combustion chamber is disposed after a first turbine stage and before a second turbine stage of the steam turbine in the direction of the flow of steam and the flow of steam in the combustion chamber can be heated by mixing it with a hot gas that can be produced in said combustion chamber.

The invention is thereby based on the consideration that the thermal transfer of a hot gas to a medium to be heated is subject to fewer limitations compared with the prior art, if the energy transfer to the medium to be heated does not use a heat exchanger surface.

This is achieved with the invention in that the flow of steam to be heated is introduced directly into a combustion chamber and is mixed directly with the hot gas there.

This claimed internal additional firing system can be used after the steam generator and before the steam turbine in the direction of the flow of steam, in other words to superheat live steam, or even to superheat steam which has already transferred some of its energy in a turbine stage and is supplied to a further turbine stage after a claimed superheating process.

Higher steam temperatures can be achieved with a claimed steam power plant than with the prior art, which can contribute to the greater efficiency of the steam power plant.

If the additional firing system implemented by means of the combustion chamber is disabled or fails in a claimed steam power plant, the steam power plant can continue to operate in the manner of a known steam power plant.

Hydrogen and/or a hydrocarbon, in particular methane, can advantageously be supplied to the combustion chamber as fuel.

In particular the fuel comprises carbon and/or hydrogen.

The use of hydrogen as fuel primarily has the advantage that—if the hydrogen is produced as is often standard practice by reforming or gasification from a hydrocarbon—any carbon dioxide occurring can be retained during production of the hydrogen in the process of reforming or gasifying a hydrocarbon, with a comparatively low energy outlay, thus preventing the formation of an acid steam mixture inside the steam turbine and/or other components of the steam power plant from the outset.

To achieve particularly efficient firing of the combustion chamber, a gas containing oxygen, in particular pure oxygen and/or air, can advantageously be supplied to the firing facility to produce a combustion atmosphere.

This embodiment of the invention takes into account the requirement that fuel combustion is only possible in a suitable combustion atmosphere. Particularly efficient combustion can be achieved by supplying pure oxygen, as compared with air this contains no components that might tend to hinder combustion, which would for example have to be separated before combustion in an air separator, to create a suitable combustion atmosphere.

In a further preferred embodiment of the invention the combustion products that occur can be removed from the flow of steam by means of a condenser connected downstream from the steam turbine.

Combustion products result from almost all combustion processes and most have to be removed, as they can be deposited in the combustion chamber or other components, particularly after a long operating period, and restrict its function.

If hydrocarbon for example is burned as fuel in an atmosphere of pure oxygen in a claimed steam power plant, the combustion products water and carbon dioxide at least result. These combustion products are carried along by the flow of steam and routed to the condenser. A condenser is generally present anyway in known steam power plants, so that a separate condenser that is suitable for removing combustion products does not have to be provided for the purposes of the invention.

When the steam, which contains the combustion products as a mixture of water and carbon dioxide, is cooled, the water element largely condenses, leaving almost pure, gaseous carbon dioxide, which can be removed from the condenser and stored for example.

As already mentioned above, when hydrogen, which is produced by reforming or gasifying a hydrocarbon, is used as fuel, any carbon dioxide occurring can be removed before the fuel is introduced into the combustion chamber, such that almost no carbon dioxide results as a combustion product during combustion in this instance.

The internal additional firing implemented by means of the combustion chamber of a claimed steam power plant can be made available very quickly during operation of the steam turbine. It only requires ignition of the fuel introduced into the combustion chamber; the time required in particular to heat up known heat exchanger surfaces in particular is not required.

A claimed steam power plant also has the advantage that combustion products and/or waste gas do not necessarily have to be removed from the combustion chamber by means of a separate discharge facility, as they are carried along with the flow of steam and can be extracted at another point in the steam circuit, for example the said condenser. Also a higher steam temperature can be achieved with the invention, without having to change the design of the steam generator.

A claimed steam power plant can in particular also be used to supply energy in peak load periods or to boost the system frequency of an electrical energy supply network; a claimed steam power plant allows fast output regulation and can be used in a very flexible manner.

BRIEF DESCRIPTION OF THE DRAWING

An exemplary embodiment of the invention is shown in the FIGURE which follows, in which:

FIGURE shows a claimed steam power plant.

DETAILED DESCRIPTION OF THE INVENTION

The FIGURE shows a claimed steam power plant 1, having a steam turbine 3 coupled to a generator 21 and a fired steam generator 5.

The steam turbine 3 has three stages, a first turbine stage 11, a second turbine stage 13 and a third turbine stage 15, which are configured as a high-pressure stage, a medium-pressure stage and a low-pressure stage.

In the present exemplary embodiment in the FIGURE the steam generator 5 is a boiler fired by coal 27, to which combustion air 29 is supplied to maintain the coal-firing process.

A heating surface 37 is disposed in the area of the hot end of the steam generator 5 and an intermediate superheating heating surface 35 is disposed in a lower temperature area.

The heating surface 37 serves to heat a water supply 24 from a water supply tank 23 in the steam generator 5 such that operating steam can be supplied to the first turbine stage 11.

After partial expansion in the first turbine stage 1 the steam is subjected to intermediate superheating by means of the intermediate superheating heating surface 35. A flow of steam 17 leaves the intermediate superheating heating surface 35 in direction 9 and is routed to a firing facility. During this process the flow of steam 17 is heated in a combustion chamber 19 by means of a fuel 33 and the introduction of oxygen 31, with the flow of steam 17 in the combustion chamber 19 mixing with the hot gas that results in the combustion chamber 19 during combustion of the fuel 33.

The thermal transfer from the hot gas to the flow of steam 17 therefore takes place directly by mixing, without a material, for example a heat exchanger surface, being provided for the thermal transfer.

It is also possible to use air instead of oxygen 31 to produce a suitable combustion atmosphere, with the air optionally being split into oxygen and residual gas by means of an air separator before introduction into the combustion chamber.

A hydrocarbon, in particular methane, or hydrogen can be used as the fuel 33.

The flow of steam 17 heated by means of the combustion chamber 19 is supplied to the second turbine stage 13, where it converts at least some of the energy contained in it to mechanical work. The thus further expanded steam leaves the second turbine stage 13 and is routed to the third turbine stage 15, where the energy still present in the steam is converted as efficiently as possible to mechanical energy.

The expanded steam leaves the third turbine stage 15 as a water/steam mixture and is routed to a condenser 25, where the steam element still present is condensed to water.

This water collecting in the condenser 25 is supplied to the water supply tank 23 as condensate 26.

Combustion products 39, which result during combustion in the combustion chamber 19, can be removed from the condenser 25.

As combustion takes place within the flow of steam 17 in the combustion chamber 19, the combustion products 39 are carried along by the flow of steam 17 in the steam circuit and removed from the condenser 25 according to this embodiment of the invention.

If a hydrocarbon is combusted with oxygen 31 as the fuel 33 for example, the combustion products 39 comprise water and carbon dioxide. This water/carbon dioxide mixture is carried along by the flow of steam 17 and can be removed from the condenser 25, as the water element is largely condensed during cooling of the water/carbon dioxide mixture, leaving a gas in the form of almost pure gaseous carbon dioxide, which can then be carried away and stored for example. 

1-4. (canceled)
 5. A steam power plant comprising; at least one steam turbine; a fired steam generator; and a combustion chamber that is disposed after a first turbine stage and before a second turbine stage of the steam turbine in the direction of the flow of steam and the flow of steam in the combustion chamber is heated by mixing it with a hot gas that is produced in the combustion chamber.
 6. The steam power plant according to claim 5, wherein hydrogen or a hydrocarbon is supplied as fuel to the firing facility.
 7. The steam power plant according to claim 5, wherein hydrogen and a hydrocarbon is supplied as fuel to the firing facility.
 8. The steam power plant according to claim 7, wherein the hydrocarbon is methane.
 9. The steam power plant according to claim 5, wherein a gas containing oxygen and/or air is supplied to the firing facility to produce a combustion atmosphere in the combustion chamber.
 10. The steam power plant according to claim 5, wherein the gas contains pure oxygen.
 11. The steam power plant according to claim 5, wherein combustion products occurring are removed from the flow of steam by a condenser connected downstream from the steam turbine. 